Les communautés végétales plus diverses sont-elles plus résistantes aux invasions ?

Early theoretical analyses and observations of community structure have led to the hypothesis that a high diversity of communities increases their resistance to invasions. However, to this date, observation and experimental data have shown positive or negative relationships between plant community diversity and invasibility. Studies of biological invasions proposed several others mechanisms explaining invasions: disturbances, presence of empty niches and interactions with others comrnunity trophic levels. The role of plant diversity can be decomposed in two factors: is specific richness per se and/or the diversity of functional groups that lead to invasion resistance of communities? A study carried out in old fields of Montpellier country showed a general picture of invasion and its complexity in this country. Our observations of these invasion patterns confirmed the difficulties to observe clear relationships with their diversity. We then resorted to serni-controlled field experiments. We sowed annual old field communities with different levels of diversity: variation in species rich ness, variation in functional richness and variation in functional identities for a fixed functional richness. Demographie and vegetative parameters of two exotic probes transplanted into these communities, Conyza bonariensis and C. canadensis, were measured along their life cycle. Primary community functioning parameters of the model ecosystems were measured simultaneously. Species richness had little effect on performance of the two Conyza species. Functional composition appeared more relevant than functional richness per se to explain community invasibility. Mechanisms of functional composition effects are proposedDes études de biologie des invasions ont conduit à l'hypothèse qu'une diversité élevée des communautés augmente leur résistance aux invasions. Les données d'observation ou expérimentales montrent une relation positive ou négative entre diversité et invasibilité des communautés végétales. Les études sur les invasions biologiques suggèrent plusieurs autres mécanismes les favorisant : les perturbations, la disponibilité de niches écologiques et les interactions avec les autres niveaux trophiques. Le rôle de la diversité biologique peut se décomposer en deux aspects : est-ce la richesse spécifique per se et/ou la diversité des groupes fonctionnels qui permet de résister aux invasions ? Une étude réalisée dans des friches de la région de Montpellier nous a permis d'avoir une vue générale du phénomène d'invasion et de sa complexité dans la région. Les résultats ont montré qu'il était difficile de mettre en évidence des patrons clairs d'invasion et de tester les mécanismes mis en jeu. Pour cette raison, deux expériences en conditions semi-contrôlées ont été réalisées. Nous avons semé des communautés annuelles présentant différents niveaux de diversité : variation de la richesse spécifique, de la richesse fonctionnelle et de la composition fonctionnelle. Ces communautés présentaient différentes diversités spécifiques et fonctionnelles. À l'intérieur de ces communautés, nous avons suivi les paramètres démographiques et végétatifs de deux espèces exotiques congénériques, Conyza canadensis et C. bonariensis introduites au stade plantule. Des mesures des paramètres du fonctionnement des communautés ont été réalisées simultanément. Les résultats montrent que la composition fonctionnelle de la communauté est plus importante que la richesse per se. De plus, ces résultats nous ont permis d' approcher les mécanismes impliqués dans la résistance des communautés végétales aux invasion

Integrative policy development for healthier people and ecosystems : a European case analysis

There is growing evidence of the inter‐relationships between ecosystems and public health. This creates opportunities for the development of cross‐sectoral policies and interventions that provide dual benefits to public health and to the natural environment. These benefits are increasingly articulated in strategy documents at national and regional level, yet implementation of integrative policies on the ground remains limited and fragmented. Here, we use a workshop approach to identify some features of this evidence–implementation gap based on policy and practice within a number of western European countries. The driving forces behind some recent moves towards more integrative policy development and implementation show important differences between countries, reflecting the non‐linear and complex nature of the policy‐making process. We use these case studies to illustrate some of the key barriers to greater integrative policy development identified in the policy analysis literature. Specific barriers we identify include: institutional barriers; differing time perspectives in public health and ecosystem management; contrasting historical development of public health and natural environment disciplinary policy agendas; an incomplete evidence base relating investment in the natural environment to benefits for public health; a lack of appropriate outcome measures including benefit–cost trade‐offs; and finally a lack of integrative policy frameworks across the health and natural environment sectors. We also identify opportunities for greater policy integration and examples of good practice from different countries. However, we note there is no single mechanism that will deliver integrative policy for healthier people and ecosystems in all countries and situations. National governments, national public agencies, local governments, research institutions, and professional bodies all share a responsibility to identify and seize opportunities for influencing policy change, whether incremental or abrupt, to ensure that ecosystems and the health of society are managed so that the interests of future generations, as well as present generations, can be protected

Identification of a BRCA2-Specific modifier locus at 6p24 related to breast cancer risk

Common genetic variants contribute to the observed variation in breast cancer risk for BRCA2 mutation carriers; those known to date have all been found through population-based genome-wide association studies (GWAS). To comprehensively identify breast cancer risk modifying loci for BRCA2 mutation carriers, we conducted a deep replication of an ongoing GWAS discovery study. Using the ranked P-values of the breast cancer associations with the imputed genotype of 1.4 M SNPs, 19,029 SNPs were selected and designed for inclusion on a custom Illumina array that included a total of 211,155 SNPs as part of a multi-consortial project. DNA samples from 3,881 breast cancer affected and 4,330 unaffected BRCA2 mutation carriers from 47 studies belonging to the Consortium of Investigators of Modifiers of BRCA1/2 were genotyped and available for analysis. We replicated previously reported breast cancer susceptibility alleles in these BRCA2 mutation carriers and for several regions (including FGFR2, MAP3K1, CDKN2A/B, and PTHLH) identified SNPs that have stronger evidence of association than those previously published. We also identified a novel susceptibility allele at 6p24 that was inversely associated with risk in BRCA2 mutation carriers (rs9348512; per allele HR = 0.85, 95% CI 0.80-0.90, P = 3.9×10−8). This SNP was not associated with breast cancer risk either in the general population or in BRCA1 mutation carriers. The locus lies within a region containing TFAP2A, which encodes a transcriptional activation protein that interacts with several tumor suppressor genes. This report identifies the first breast cancer risk locus specific to a BRCA2 mutation background. This comprehensive update of novel and previously reported breast cancer susceptibility loci contributes to the establishment of a panel of SNPs that modify breast cancer risk in BRCA2 mutation carriers. This panel may have clinical utility for women with BRCA2 mutations weighing options for medical prevention of breast cancer

An original phylogenetic approach identified mitochondrial haplogroup T1a1 as inversely associated with breast cancer risk in BRCA2 mutation carriers

Introduction: Individuals carrying pathogenic mutations in the BRCA1 and BRCA2 genes have a high lifetime risk of breast cancer. BRCA1 and BRCA2 are involved in DNA double-strand break repair, DNA alterations that can be caused by exposure to reactive oxygen species, a main source of which are mitochondria. Mitochondrial genome variations affect electron transport chain efficiency and reactive oxygen species production. Individuals with different mitochondrial haplogroups differ in their metabolism and sensitivity to oxidative stress. Variability in mitochondrial genetic background can alter reactive oxygen species production, leading to cancer risk. In the present study, we tested the hypothesis that mitochondrial haplogroups modify breast cancer risk in BRCA1/2 mutation carriers. Methods: We genotyped 22,214 (11,421 affected, 10,793 unaffected) mutation carriers belonging to the Consortium of Investigators of Modifiers of BRCA1/2 for 129 mitochondrial polymorphisms using the iCOGS array. Haplogroup inference and association detection were performed using a phylogenetic approach. ALTree was applied to explore the reference mitochondrial evolutionary tree and detect subclades enriched in affected or unaffected individuals. Results: We discovered that subclade T1a1 was depleted in affected BRCA2 mutation carriers compared with the rest of clade T (hazard ratio (HR) = 0.55; 95% confidence interval (CI), 0.34 to 0.88; P = 0.01). Compared with the most frequent haplogroup in the general population (that is, H and T clades), the T1a1 haplogroup has a HR of 0.62 (95% CI, 0.40 to 0.95; P = 0.03). We also identified three potential susceptibility loci, including G13708A/rs28359178, which has demonstrated an inverse association with familial breast cancer risk. Conclusions: This study illustrates how original approaches such as the phylogeny-based method we used can empower classical molecular epidemiological studies aimed at identifying association or risk modification effects.Peer reviewe

Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk

BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7×10-8, HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4×10-8, HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4×10-8, HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific associat

Les communautés végétales plus diverses sont-elles plus résistantes aux invasions ? Une approche expérimentale dans les friches méditerranéennes

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Les communautés végétales plus diverses sont-elles plus résistantes aux invasions ?

Early theoretical analyses and observations of community structure have led to the hypothesis that a high diversity of communities increases their resistance to invasions. However, to this date, observation and experimental data have shown positive or negative relationships between plant community diversity and invasibility. Studies of biological invasions proposed several others mechanisms explaining invasions : disturbances, presence of empty niches and interactions with others community trophic levels. The role of plant diversity can be decomposed in two factors : is specific richness per se and/or the diversity of functional groups that lead to invasion resistance of communities ? A study carried out in old fields of Montpellier country showed a general picture of invasion and its complexity in this country. Our observations of these invasion patterns confirmed the difficulties to observe clear relationships with their diversity. We then resorted to semi-controlled field experiments. We sowed annual old field communities with different levels of diversity : variation in species richness, variation in functional richness and variation in functional identities for a fixed functional richness. Demographic and vegetative parameters of two exotic probes transplanted into these communities, Conyza bonariensis and C. canadensis, were measured along their life cycle. Primary community functioning parameters of the model ecosystems were measured simultaneously. Species richness had little effect on performance of the two Conyza species. Functional composition appeared more relevant than functional richness per se to explain community invasibility. Mechanisms of functional composition effects are proposed.Des études de biologie des invasions ont conduit à l’hypothèse qu’une diversité élevée des communautés augmente leur résistance aux invasions. Les données d’observation ou expérimentales montrent une relation positive ou négative entre diversité et invasibilité des communautés végétales. Les études sur les invasions biologiques suggèrent plusieurs autres mécanismes les favorisant : les perturbations, la disponibilité de niches écologiques et les interactions avec les autres niveaux trophiques. Le rôle de la diversité biologique peut se décomposer en deux aspects : est-ce la richesse spécifique per se et/ou la diversité des groupes fonctionnels qui permet de résister aux invasions ? Une étude réalisée dans des friches de la région de Montpellier nous a permis d’avoir une vue générale du phénomène d’invasion et de sa complexité dans la région. Les résultats ont montré qu’il était difficile de mettre en évidence des patrons clairs d’invasion et de tester les mécanismes mis en jeu. Pour cette raison, deux expériences en conditions semi-contrôlées ont été réalisées. Nous avons semé des communautés annuelles présentant différents niveaux de diversité : variation de la richesse spécifique, de la richesse fonctionnelle et de la composition fonctionnelle. Ces communautés présentaient différentes diversités spécifiques et fonctionnelles. À l’intérieur de ces communautés, nous avons suivi les paramètres démographiques et végétatifs de deux espèces exotiques congénériques, Conyza canadensis et C. bonariensis introduites au stade plantule. Des mesures des paramètres du fonctionnement des commu¬ nautés ont été réalisées simultanément. Les résultats montrent que la composition fonctionnelle de la communauté est plus importante que la richesse per se. De plus, ces résultats nous ont permis d’approcher les mécanismes impliqués dans la résistance des communautés végétales aux invasions.Prieur-Richard Anne-Hélène, Lavorel Sandra. Les communautés végétales plus diverses sont-elles plus résistantes aux invasions ? . In: Revue d'Écologie. Supplément n°7, 2000. pp. 37-51